Devices are often mounted on the perimeter surface of vertebral bodies during surgery. Examples include attaching a plate or ligament to connect adjacent vertebral bodies. It is important that the device be properly positioned along the vertebrae, and that the device be firmly attached to the vertebral body. These two aspects will result in the device operating properly, and to cause more consistent and expected results. Poor placement or attachment may cause the device to not operate properly, or move relative to the vertebral body. These occurrences result in either pain to the patient, or may result in the device failing or breaking free from the vertebral body.
Proper alignment and attachment of the devices is often difficult because of variations in the shape and contours of the vertebral body. Poor surface contact between the device and the vertebral body results if the device is mounted over variations in the surface of the vertebral body. It is not necessary that the entire device surface contact the vertebral body, but better results are obtained by greater contact. Poor surface contact may result in the over-stressing the fasteners or device that attach to the vertebral body. This in turn may result in the fasteners pulling loose from the vertebral body, or the device or the fasteners failing. Either of these results is detrimental to the patient.
It may be more difficult for the surgeon to mount the device if there is not an adequate mounting surface on the vertebral body. The surgeon may be forced to mount the device in an area other than the preferred location on the vertebral body. This may result in the device not operating to the fullest capacity. The non-preferred placement may also be a more difficult procedure for the surgeon which may require a higher degree of skill, or possibly take a longer time to complete.
The present invention is directed to a system and method of contouring a perimeter surface of a vertebral body. The invention comprises positioning a reference mechanism relative to one or more vertebral bodies. In one embodiment, the reference mechanism is positioned relative to the disc space between adjacent vertebral bodies. The reference mechanism may have a variety of forms, including mechanical, computerized, and visual. A bone removal mechanism is aligned with the reference mechanism to contour the vertebral body or bodies. A predetermined relationship exists between the bone removal mechanism and the reference mechanism. The predetermined relationship provides for the bone removal mechanism to contour the vertebral body or bodies in a precise fashion.
In one embodiment, the device includes a trial and a bone surface preparation device. The trial may include a spacer having first and second contact surfaces that are spaced a distance apart to contact end plates of adjacent vertebral bodies. A guide may extend outward from the spacer at a variety of angles depending upon the specific application for the device. The bone surface preparation device may be a cannulated member having an opening that extends over the guide. The device may include a cutting head having a blade that extends the entire section around the opening, or at least around a portion of the section.
In use, one method includes inserting the trial into the patient with the spacer positioned between adjacent vertebral bodies and the guide extending outward. The bone surface preparation device may be inserted over the guide and slid down to a point where the blade contacts the perimeter surface of at least one of the vertebral bodies. The device may then be powered such that the blade rotates and the blade shapes and contours the perimeter surface of one or both of the vertebral bodies.